UNIVERSITY  OF   CALIFORNIA 

COLLEGE   OF  AGRICULTURE 

BERKELEY 


AGRICULTURAL  EXPERIMENT  STATION 
8ENJ.    IDC    WHEELER,    President 
THOMAS    FORSYTH     HUNT,    DEAN   AND    DlWECTOd 
H.     E.    VAN     NORMAN,    VlCE-DlR  ECTOR    AND    DEAN 
University    Farw    School 


CIRCULAR  No.  157 

(November,  1916) 


CONTROL  OF  PEAR  SCAB 


By  RALPH  E.  SMITH 


This  circular  is  published  on  account  of  the  unusual  prevalence  of 
pear  scab  in  California  in  1916  and  the  fact  that  our  bulletin  163  has 


Fig.  1. — Pear  scab. 


long  been  out  of  print.  Growers  who  have  observed  the  following 
directions  explicitly  year  after  year  have  had  little  or  no  trouble  from 
scab. 

1.  Plow  under  dead  leaves  as  thoroughly  as  possible. 

2.  Spray  with  Bordeaux  mixture  twice  while  the  buds  are  unfold- 
ing, first  when  the  leaf  buds  are  just  opening,  as  in  Figure  3 ;  second, 
a  week  or  ten  days  later,  just  before  the  individual  blossoms  open,  as 


Fig.  2. — First  stage  in  opening  of  pear  tree  buds.    A  little  early  for  spraying. 

in  Figures  4  to  5.    The  first  spraying  is  the  more  important,  but  both 
should  be  given. 

3.  In  large  orchards  begin  spraying  when  the  buds  are  about  like 
those  which  are  open  the  least  in  Figure  3,  so  that  if  delays  occur  the 
trees  will  get  at  least  one  good  spraying  before  it  is  too  late.  Spraying 
before  the  first  stage,  Figure  2,  or  after  the  last,  Figure  5,  will  do  little 
or  no  good  in  scab  control,  especially  with  Bartletts. 

4.  As  an  extra  precaution,  make  a  third  scab  spraying  by  mixing 
the  first  lead  arsenate  codling  moth  spray  with  Bordeaux  mixture  in- 
stead of  plain  water. 

5.  Spray  with  good  equipment  and  high  pressure,  and  cover  the 
trees  thoroughly,  especially  the  twigs  and  buds. 


Fig.  3. — Further  development  of  buds. 
COMMENCE  FIRST  SPRAYING 


Fig.  4. — Blossom  buds  appearing. 
COMMENCE  SECOND  SPRAYING 


Fig.  5. — Blossom  buds  well  out.     Second  spraying  should  be  finished. 

Directions  for  Making  Bordeaux  Mixture 

Bluestone  20  lbs. 

Quicklime    25  lbs. 

Water 200  gals. 

Dissolve  the  bluestone  and  slake  the  lime  in  separate  vessels. 
Strain  the  bluestone  into  the  spray  tank  and  fill  it  half  full  or  more 
with  water.  Strain  in  the  lime  mixed  with  the  rest  of  the  water. 
Always  have  the  materials  well  diluted  before  mixing  them  together. 

(Note. — If  a  third  spraying,  of  lead  arsenate  combined  with  Bor- 
deaux mixture,  be  made,  the  amounts  of  bluestone  and  lime  may  be 
reduced  to  15  and  20  pounds,  respectively.) 


